Maximizing Quantum Enhancement in Axion Dark Matter Experiments

TL;DR

This paper compares linear amplifiers and microwave photon-counters in axion dark matter detection, highlighting conditions where photon counters outperform amplifiers and proposing methods to enhance scan rates.

Contribution

It provides a comprehensive analysis of detector performance in axion experiments, introducing new strategies like off-resonance background reduction and over-coupling regimes.

Findings

Photon counters are advantageous at high frequencies and low backgrounds.

Off-resonance background reduction can improve scan rates.

Over-coupling resonators up to β~10 enhances detection capabilities.

Abstract

We provide a comprehensive comparison of linear amplifiers and microwave photon-counters in axion dark matter experiments. The study is done assuming a range of realistic operating conditions and detector parameters, over the frequency range between 1--30 GHz. As expected, photon counters are found to be advantageous under low background, at high frequencies ($\nu>$ 5 GHz), if they can be implemented with robust wide-frequency tuning or a very low dark count rate. Additional noteworthy observations emerging from this study include: (1) an expanded applicability of off-resonance photon background reduction, including the single-quadrature state squeezing, for scan rate enhancements; (2) a much broader appeal for operating the haloscope resonators in the over-coupling regime, up to $\beta\sim 10$; (3) the need for a detailed investigation into the cryogenic and electromagnetic conditions inside haloscope cavities to lower the photon temperature for future experiments; (4) the necessity to develop a distributed network of coupling ports in high-volume axion haloscopes to utilize these potential gains in the scan rate.